Cannot delete old backup data by using bootable media

Hi, I'm using Acronis True Image 2016. Now There is enough space in the partition for storing the backup data. So I tried to delete old backup data by using bootable media. I go to "Recovery section" and press "Refresh backups" in the rescue tool. And I right-click the backup data to delete and click "Delete" in the pop-up menu. However, Deletion is not performed.

There is no need to use the Acronis bootable Rescue Media to delete your unwanted backup data.

You can delete such backups using Windows Explorer but after doing so, you should then perform a Validation for the Acronis backup tasks that created the files which have been removed. This is needed to reconcile the internal Acronis database, and would still be needed if deleting files using the rescue media.